v3.21.2
Regulation and Capital Adequacy - Changes in Risk-weighted Assets (Detail) - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Standardized Capital Rules [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Risk-Weighted Assets, Beginning balance $ 554,162 $ 563,575
Change in Credit RWAs 45,613 (13,549)
Change in Market RWAs 21,560 4,136
Risk-Weighted Assets, end of period 621,335 554,162
Standardized Capital Rules [Member] | Derivatives [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 8,538 (614)
Standardized Capital Rules [Member] | Commitments Guarantees and Loans [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 20,650 (3,239)
Standardized Capital Rules [Member] | Securities Financing Transactions [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 6,360 5,560
Standardized Capital Rules [Member] | Equity Investments [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 8,634 (9,870)
Standardized Capital Rules [Member] | Other [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 1,431 (5,386)
Standardized Capital Rules [Member] | Regulatory VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 858 5,980
Standardized Capital Rules [Member] | Stressed VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 19,939 1,067
Standardized Capital Rules [Member] | Incremental Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs (178) 3,574
Standardized Capital Rules [Member] | Comprehensive Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 406 365
Standardized Capital Rules [Member] | Specific Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 535 (6,850)
Advanced Capital Rules [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Risk-Weighted Assets, Beginning balance 609,750 544,653
Change in Credit RWAs 32,933 51,634
Change in Market RWAs 21,560 4,338
Change in operational risk 2,900 9,125
Risk-Weighted Assets, end of period 667,143 609,750
Advanced Capital Rules [Member] | Derivatives [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (1,559) 39,060
Advanced Capital Rules [Member] | Commitments Guarantees and Loans [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 17,209 17,131
Advanced Capital Rules [Member] | Securities Financing Transactions [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs (1,205) 2,734
Advanced Capital Rules [Member] | Equity Investments [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 12,737 (12,624)
Advanced Capital Rules [Member] | Other [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Credit RWAs 5,751 5,333
Advanced Capital Rules [Member] | Regulatory VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 858 5,980
Advanced Capital Rules [Member] | Stressed VaR [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 19,939 1,067
Advanced Capital Rules [Member] | Incremental Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs (178) 3,574
Advanced Capital Rules [Member] | Comprehensive Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs 406 567
Advanced Capital Rules [Member] | Specific Risk [Member]    
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Change in Market RWAs $ 535 $ (6,850)